2 Executive summary By virtualizing the server environment, you can improve server utilization and consolidate servers onto high capacity virtual machines. This allows you to reduce the cost to maintain and manage your server infrastructure. Virtualization also allows you to migrate data and applications among servers more quickly and efficiently. The VMware ESX.0 server takes maximum advantage of available cache and memory locality as in and core virtual machine scenarios. The performance delta between the physical and virtual configuration is significantly reduced with the latest Intel Xeon X0 (Nehalem) processor over previous tests with IBM WebSphere Application Server and the Apache DayTrader application. In many cases by increasing the number of WebSphere instances and CPUs allocated to the virtual machines VMware ESX.0 outperforms the physical environment. You will find more details regarding the comparison in the following sections. This paper compares the performance of virtual and physical servers running IBM WebSphere Application Server (WAS) on HP ProLiant DL0 G server and VMware ESX.0 with Red Hat Enterprise Linux (RHEL). server. Target audience: This paper provides assistance to solution architects for configuring IBM WebSphere Application Server on VMware ESX.0. Prior knowledge of WebSphere Application Server, VMware ESX.0, Red Hat Enterprise Linux and SUSE Linux Enterprise Server is assumed. This white paper describes testing performed in Sep 00. WebSphere test configuration In order to compare the performance and scalability of WebSphere Application Server on a single physical server running the OS natively to the performance on VMware virtual machines, multiple instances of WebSphere Application Server were created both in the native and virtual configurations. The DayTrader performance benchmark application was installed and configured in all WebSphere instances. Tests were performed, and the performance throughputs were calculated, with varying numbers of WebSphere instances and core allocations to the operating system on the physical and virtual environments. The paper refers to CPU cores as CPUs in the native environment. In the virtual environment a physical core corresponds to a virtual core or a virtual CPU. Figure show the hardware configuration, which consists of ProLiant DL0 G servers used as application servers. Separate servers were used for HP LoadRunner to simulate the load for the DayTrader benchmark and for the Oracle g database server. The HP StorageWorks 00 Enterprise Virtual Array (EVA00) was used for storage. The operating system RHEL. and VMware ESX.0 were installed on the internal storage. The virtual machines were stored on EVA00 SAN storage. Hyper-threading was disabled in the BIOS of the servers running the physical and virtual environments.

6 Figure is the screenshot from VMware vsphere Client showing the virtual machine configuration. Figure. VMware vsphere client application WebSphere and OS tuning Below is a list of tuning modifications: Enabled hugepages on both virtual and physical servers. vm.nr_hugepages = Used separate vmxnet network interfaces for web server and database traffic. Allocated memory to the virtual machine so that the operating system does not use swapping. Set the minimum and maximum heap size for Java to 0M -Xms0m -Xmx0m to reduce garbage collection from the JVM. Enable large memory pages for the JVM with Xlp option. WebSphere thread and connection pools were modified for best performance. Tests were performed with the default e000 network adapter. We noticed a performance improvement of additional ~% with vmxnet network adapter. The results in the paper are with the vmxnet network adapter.

8 Relative Performance Throughput LoadRunner was used to generate the load and the number of transactions processed by the application servers was calculated for comparison. WebSphere with single instance Figure compares the relative performance of the physical and virtual server environments when running the DayTrader benchmark on a single instance of WebSphere Application Server with varying core or virtual CPU allocations. Figure. Single instance physical and virtual comparison Virtual to Physical Single Instance Relative Performance Throughput 00% 0% 00% 0% 00% % 0 0 -% -0% Physical cores Virtual cores 0% 00% 0% 00% 0% -% % % Perf difference Physical cpu utilization Virtual cpu utilization 0% # of Physical or Virtual cores Depending on the number of cores or virtual CPU s allocated, the VMware ESX.0 virtual environment in some cases exceeds the performance of physical environment, as shown in cores and cores configuration of about % and % respectively. The virtual operating system takes maximum advantage of available cache and memory locality as shown in case of and cores performance data. The performance delta between the physical and virtual configuration is significantly reduced with the latest Intel Xeon X0 processor over previous tests with WebSphere and the DayTrader application. The performance degradation in virtual environment with core, cores and cores case is about %, % and 0% respectively. The percentage throughput difference is calculated in relation to core virtual machine performance. Due to an unidentified bottleneck the tests were unable to saturate the CPU on and cores.

9 Relative Scalability Physical and virtual CPU scalability Figure shows the scalability characteristics for virtual and physical environments are similar as the number of active cores increase from one, to two, four and six. As shown in the graph below, the scalability data indicates that both environments can achieve proportionally equivalent throughput gains with additional CPU cores and associated caches. Figure. Scalability of virtual and physical CPUs. Virtual and Physical Single Instance CPU Scalability Virtual Physical # of Physical or Virtual cores Response times The amount of time it takes to complete one transaction decreases as the number of CPUs increase. The response time in the virtual environment decreases from ms with CPU to ms with CPUs. Figure shows the response times with various physical and virtual CPU allocations. Depending on your response time requirements, the number of CPUs can be increased to match the specific requirements.

10 Response Time in ms Figure. Comparing response times 0 Virtual and Physical Single Instance Response Time Virtual Physical # of Virtual or Physical cores WebSphere with multiple instances The following section evaluates the performance results for various multi-instance and multi-vm scenarios. The VMware ESX.0 configurations include virtual machines with two, four and eight virtual CPUs. Each VM has a single instance of WebSphere Application Server. The operating system and WebSphere configuration are the same in both virtual and physical environments. -way physical and virtual comparison This section compares the physical and virtual performance with four CPUs per WebSphere instance. Figure shows the relative throughput in these cases. With one WebSphere instance, the physical configuration used cores, while the virtual configuration used one VM with vcpus. With two WebSphere instances, the physical configuration used cores, while the virtual configuration used two VMs with vcpus each. When running with one instance, the virtual configuration outperformed the physical by %. With two instances, which used all eight cores available on the server, the virtual configuration outperformed the physical by %. 0

11 Relative Performance Figure. core physical to virtual relative throughput comparison 00% 00% -way Physical to Virtual Multiple Instances Relative Performance Throughput % 00% 00% 00% % Physical Virtual 00% 0% # of WebSphere instances -way physical and virtual comparison This section compares the physical and virtual performance with two CPUs per WebSphere instance. Figure 0 shows the relative throughput in these cases. With one WebSphere instance, the physical configuration used cores, while the virtual configuration used one VM with vcpus. With two WebSphere instances, the physical configuration used cores, while the virtual configuration used two VMs with vcpus each. With four WebSphere instances, the physical configuration used all eight cores, while the virtual configuration used four VMs with vcpus each. When running with one instance, the virtual configuration outperformed the physical by %. With two instances the virtual configuration outperformed the physical by %. With four instances, which used all eight cores available on the server, the physical configuration outperformed the virtual by %.

13 Summary Virtualization is an excellent way to increase server utilization. However, care should be taken on how the CPU and memory resources are allocated to the virtual machines. Performance might degrade with improper allocation of resources. The system resources should be monitored to check if swapping is taking place on the virtual machine. If so, increase the memory allocation for the virtual machine. Over committing the memory on the virtual machines will degrade the performance considerably. Using the vmxnet network adapter for the virtual machines will provide better performance than the default e000 network adapter. As seen in the tests, VMware ESX.0 performance is at most % less than the physical server. In many cases VMware ESX.0 outperforms the physical environment. The gap between the environments can be reduced by increasing the number of instances and CPUs allocated to the virtual machines. Both virtual and physical environments provide incremental performance gains as the number of active CPUs are increased.

14 For more information HP ProLiant servers, IBM WebSphere, Red Hat Enterprise Linux, SUSE Linux Enterprise, VMware ESX server, Apache DayTrader.0 Benchmark Sample, To help us improve our documents, please provide feedback at Technology for better business outcomes Copyright 00 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. The only warranties for HP products and services are set forth in the express warranty statements accompanying such products and services. Nothing herein should be construed as constituting an additional warranty. HP shall not be liable for technical or editorial errors or omissions contained herein. Intel and Xeon are trademarks of Intel Corporation in the U.S. and other countries. Java is a US trademark of Sun Microsystems, Inc. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. VMware is a registered trademark or trademark of VMware, Inc. in the United States and/or other jurisdictions. AA0-ENW, January 00

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